php 一维数组变多维

将下面的数组处理成下图的样子

$arr = [\'a\', \'b\', \'c\', \'d\',\'e\',\'f\'];

<?php

$arr = [\'a\', \'b\', \'c\', \'d\',\'e\',\'f\'];

$x = [];
$y = &$x; 
$value = 1234;

while ($key = current($arr)) {
    $y[$key] = [];

    $y = &$y[$key];
    next($arr);
    //echo $key;
}
$y = $value;

print_r($x);
?>